Lubricant compositions and methods

ABSTRACT

Abstract of Disclosure 
     A lubricant composition is disclosed comprising a superabsorbent polymer combined with a material for decreasing friction between moving surfaces.  The superabsorbent polymer absorbs from about 25 to greater than 100 times its weight in water and may comprise a polymer of acrylic acid, an acrylic ester, acrylonitrile or acrylamide, including co-polymers thereof or starch graft co-polymers thereof or mixtures thereof.  In the composition, the  material for decreasing friction comprises a petroleum lubricant containing an additive, water containing an additive, synthetic lubricant, grease, solid lubricant or metal working lubricant, wherein the synthetic lubricant, grease, solid lubricant or metal working lubricant optionally contain an additive.  A method of lubricating a surface is also disclaosed comprising coating said surface with the lubricating composition comprising the superabsorbent polymer combined with a material for decreasing friction between moving surfaces, wherein the material for decreasing friction comprises a petroleum lubricant, water, synthetic lubricant, grease, solid lubricant or metal working lubricant, and optionally an additive.

Cross Reference to Related Applications

[0001] This application is a continuation of U.S. Application Serial No.08/487,436, filed June 7, 1995.

Detailed Description

[0002] Field of the Invention

[0003] The field of the invention is lubricants and especially lubricantcompositions comprising a superabsorbent polymer in combination with alubricant material.

[0004] Description of Related Art

[0005] Lubricant materials function by separating moving surfaces tominimize friction and wear. Archeological evidence dating to before 1400B.C. shows the use of tallow to lubricate chariot wheel axles. Leonardoda Vinci discovered the fundamental principles of lubrication andfriction, but lubrication did not develop into a refined science untilthe late 1880's in Britain when Tower produced his studies on railroadcar journal bearings in 1885. In 1886 Reynolds developed this into atheoretical basis for fluid film lubrication.

[0006] Lubrication principles vary from the separation of movingsurfaces by a fluid lubricant through boundary lubrication, to drysliding. In many respects, these principals are coextensive.

[0007] Fluid Film Lubrication

[0008] In fluid film lubrication, the load on moving surfaces issupported entirely by the fluid between the surfaces which is a filmunder pressure. The pressure on the film develops through the motion ofthe surfaces, which in turn delivers the lubricant into a convergingwedge-shaped zone. The behavior of the moving surfaces is totallydependent on the fluidity or viscous behavior of the lubricant. Filmpressure and power loss are dependent on the viscosity of the lubricantas well as the configuration of the moving surfaces, and lubricant shearstrength. Hydrodynamic or squeeze-film action cannot provide adequateload support in some instances for bearings lubricated with oil orwater. Pumping the lubricant into the moving surfaces sometimes providesthe necessary hydrodynamic or squeeze-film properties for bearings usedfor handling heavy loads in low speed equipment. This practice isespecially common with low viscosity lubricants such as water. It wouldtherefore be advantageous to provide additives to these types oflubricants to overcome these difficulties.

[0009] Oil film lubricants on surfaces are limited in their lubricatingcapabilities and as such have load limits. Asperities or high spots onthe moving surfaces will in turn support the load when the load limit ofthe lubricant is reached so that the lubrication moves from full-film tomixed-film to complete boundary lubrication with an increase incoefficient of friction between the moving surfaces. High load, lowspeed, low viscosity lubricants, misalignment, high surface roughness oran inadequate supply of lubricant causes this change from full-film toboundary lubrication. Chemical additives, however, can reduce resultantwear and friction.

[0010] Surface contact through asperities on the moving surfaces canresult in tearing of the surfaces and is especially a problem withincreasing loads. Plastic deformation, temperature buildup and weldingof the surfaces with eventual seizure of the surfaces occurs as aresult. This problem is especially prevalent in hypoid gears used inautomobile differentials. Extreme pressure lubricants combat welding ofthe surfaces in these circumstances and contain organic compounds thatreact at these elevated temperatures and form high-melting inorganiclubricant films on the surfaces. Sulfur, chlorine, phosphorous and leadcompounds in these additives provide low shear strength layers thatminimize surface tearing, or coat the moving surfaces to prevent fusing.Since extreme pressure additives function by chemical action, they arenot used where the metal surfaces will be severely eroded. Increasingthe lubricant or oil viscosity by means of an additive, lowering theunit bearing loading, improving the finish on the moving surfaces anduse of external pressurization offer alternatives to extreme-pressureadditives.

[0011] Dry rubbing or dry sliding involving solid-to-solid contactoccurs in fluid lubrication systems as for example in machine start-up,run-in misalignment or inadequate clearance, reversal of direction ofmoving surfaces, or any unforeseen or unplanned interruptions inlubricant delivery. Conventional lubricants such as greases or oils alsoare not used on moving surfaces in extreme temperature, high vacuum,radiation or contamination environments. Dry lubricants applied as thincoatings or as particulate materials in these environments reduce wearand friction of moving surfaces. These films or particulate materialsmay comprise or incorporate solid or particulate carbon-graphite, leadbabbitt, bronze, aluminum, polyethylene or polytetrafluoroethylene solidor particulate materials in a binder where the film or particulates areadhered to one or both of the moving surfaces. The effectiveness of thedry lubricant film or particulates is controlled to some degree by thebinder where solid or particulate lubricants are employed as well asconditions of use such as the load, surface temperatures generatedduring use, speed of the moving surfaces, hardening, fatigue, welding,recrystallization, oxidation and hydrolysis. It would be an advantagetherefore to have a binder that was strongly adherent and resistant tosome of the conditions generated while in use.

[0012] In elastohydrodynamic lubrication carrying the load on rollingcontacts in ball and roller bearings, gear teeth, cams or frictiondrives, minimizes lubrication problems. Focusing the load on a smallcontact area on these moving surfaces results in high elastic contactstresses. Lubricant films help support the load which is described as"elastohydrodynamic," because of the close relationship between theformation of a thin hydrodynamic fluid lubricant film and elasticdeformation.

[0013] The lubricant viscosity and film conditions at the entry of thecontact zone in these systems generally fix the lubricant film thicknesswhich is substantially uniform over most of its length along thecontact. It is believed that high contact pressures lead to excessivelubricant viscosity and pressure distribution close to the Hertz patternfor simple static elastic contact theory. It has also been noted thatonly a slight reduction in film thickness results with increasing loadswith pronounced contact deformation. In plotting contact pressure in psi(pounds per square inch)against distance and direction of lubricantflow, it appears that optimum lubricity is obtained with a sharppressure spike at the exit portion of the lubricant film; however, thisdoes not take into account changes in temperature, relaxation time orother variables in the lubricating system. It would therefore be anadvantage to provide an additive that would enhance viscosity and filmformation and retention under these and other conditions.

[0014] Load capacity with a full elastohydrodynamic film is limited byfatigue strength of the moving surfaces in rolling contact systems. Theworking of grain boundaries beneath the contact surface, where shearstress is at a maximum, generates damage. Fatigue cracks occur withinthis heavily stressed zone with repeated stress cycles. Particles areloosened, which is characterized as surface flaking, and represents thedepth of the zone of maximum shear stress. The fatigue cracks arestarted by focal points of oxide particles and stringers of impurities.

[0015] Where the lubricant film thickness becomes less than the surfacefinish of the moving or rolling surfaces, under high load, low speed orlow lubricant viscosity, boundary lubrication comes into play which isdependent upon the chemical nature of the lubricant. The drop in fatiguelife can be avoided under such conditions as well as surface wear withthe proper lubricant additives.

[0016] Petroleum Lubricants

[0017] Petroleum based lubricants are extensively used because of theirwide availability and consequent low cost. Petroleum lubricants are wellknown in the art and generally comprise low viscosity and low densityparaffins having relatively high freezing points. When combined withoxidation inhibitors to obtain high temperature stability, oxidationresistance is improved and sludging tendency is minimized.

[0018] Aromatic petroleum lubricants such as napthenes are generallyoxidation stable but form insoluble sludges at high temperatures.Naphthenic oils have low pour point, low oxidation stability andproperties between paraffins and aromatics. They are also present inparaffin lubricants to a small degree. Naphthenic oils, however, ornaphthenes are used by themselves in combination with oxidationinhibitors. It therefore would be advantageous to provide additives thatminimize these difficulties.

[0019] Representative petroleum lubricating oils include SAE types 10W,20W, 30, 40, 50, 10W-30, 20W-40, 75, 80, 90 140, 250 and so-calledautomatic transmission fluids.

[0020] Additives

[0021] Various additives mixed with lubricating materials help meet therequirements of modern automobile engines, high-speed machinery,high-pressure hydraulic systems, torque converters, aircraft engines,turbine engines, steam engines, steam turbines, electric motors,hydraulic systems and the like.

[0022] Petroleum lubricants and other so-called oil-type lubricantsemploy sulfur, nitrogen or phosphorous type organic compounds, andalkylphenols as antioxidants or oxidation inhibitors. Hydroperoxidesinitially formed in the oil during oxidation lead to the subsequentproduction of organic acids and other oxygen containing organiccompounds. Antioxidants either inhibit the formation of, or complex,hydroperoxides to minimize the formation of acids, sludge and varnish.

[0023] Some commonly employed oxidation inhibitors for steam turbines,electric motors and hydraulic systems include 2-naphthol,di-t-butyl-p-cresol and phenyl-1-naphthylamine. Thiophosphates such aszinc, barium, and calcium thiophosphate are also widely used asantioxidants in lubricating oils for automobile and truck engines.

[0024] Alkylsuccinic type acids and other mildly polar organic acids ororganic amines are employed as rust inhibitors as well as organicphosphates, polyhydric alcohols, sodium sulfonates and calciumsulfonates.

[0025] Many antiwear compounds, generally well known in the art, improveboundary film lubrication, and are classified into seven main groups.The first comprises compounds containing oxygen, such as fatty acids,esters and ketones; the second comprises compounds containing sulfur orcombinations of sulfur and oxygen; the third comprises organic chlorinecompounds such as chlorinated wax; the fourth includes organic sulfurcompounds such as sulphurized fats and sulphurized olefins; the fifthcomprises compounds containing both chlorine and sulfur; the sixth,compounds containing organic phosphorous compounds such as tricresylphosphate, thiophosphates, and phosphites; and the seventh, organic leadcompounds such as tetraethyl lead. The use of olefins for lubricatingaluminum moving surfaces and iodine for high temperature alloys has alsobeen described in the art.

[0026] Antiwear agents employed in boundary lubricants include mildlypolar organic acids such as alkylsuccinic type acids and organic amines.Tricresyl phosphate or zinc dialkyldithiophosphate additives areemployed in lubricants for hydraulic pumps, gears and torque converterswhereas severe rubbing conditions encountered in high loadmetal-to-metal moving surfaces require lubricants and especially oiltype lubricants containing active sulfur, chlorine and lead compounds.These extreme-pressure additives enter into a chemical reaction to formcompounds on the surface of the metal moving parts such as lead sulfide,iron chloride or iron sulfide.

[0027] Detergents and dispersants are employed in lubricants andfunction by adsorption on any insoluble particles formed by the movingor sliding contact of two or more surfaces, and maintain the particlesin suspension in the lubricant. This minimizes deposits on the movingsurfaces and enhances the cleanliness of the moving surfaces. Detergentssuch as alkyl methacrylate polymers having polar nitrogen groups in theside chain are generally employed and are well known in the art.

[0028] The addition of pour-point depressants such as polymethacrylatesor wax with naphthalene or wax phenol condensation products alsoimproves the properties of lubricants.

[0029] Many lubricants also contain viscosity-index improvers such aspolyisobutylenes, polymethacrylates and poly(alkylstyrenes) having amolecular weight of from about 5000 to 20,000. The addition of foaminhibitors such as methyl silicone polymers in lubricating fluids andespecially oil type lubricants reduces frothing.

[0030] Synthetic Lubricants

[0031] Another class of lubricants comprises synthetic oils such as lowmolecular weight polymerized olefins, ester lubricants, polyglycols andsilicones, all of which are widely known in the art. Other syntheticoils include tricresyl phosphate, silicones, other organic phosphates,polyisobutylene, polyphenyl ethers, silicates, chlorinated aromatics,and fluorocarbons.

[0032] The silicone lubricants generally comprise low molecular weightpolymers or di-organo substituted silicon oxide where the organo groupsare ethyl groups, phenyl groups or mixtures thereof and are formulatedeither as room temperature liquids having the viscosity of oil orcompounded into greases. The chlorophenyl methyl silicone oils areespecially suitable.

[0033] Organic esters generally comprise diesters based on thecondensation of long chain diacids having from about 6 to about 10carbon atoms such as adipic, azelaic or sebacic acid with branched-chainalcohols having from about 8 to about 9 carbon atoms. Higher temperaturelubricants employed for turbines and especially jet engines compriseesters of trimethylolpropane or pentaerytheritol with these acids.Polymethacrylates thickening agents, sometimes added in amounts up toabout 5%, increase the viscosity of these fluids, which is somewhatlower than petroleum oils.

[0034] The polyglycol lubricants comprise those based on polypropyleneglycol prepared from propylene oxide and contain terminal hydroxylgroups. These are water insoluble lubricants. Mixtures of propylene andethylene oxides in the polymerization process will produce a watersoluble polymer, also used as a lubricant. Liquid or oil typepolyglycols have lower viscosities and molecular weights of about 400,whereas 3,000 molecular weight polyglycols are viscous polymers at roomtemperature. The use of mono- or polyhydric, such as dihydric, alcoholsin the ethylene oxide and/or propylene oxide polymerization results inthe formation of mono- or diethers which yield a different class ofpolyglycols. Esterifying the hydroxyl groups in the polyols with low orhigh molecular weight acids, i.e., those having up to about 18 carbonatoms gives another variety of polyglycol lubricants.

[0035] The polyglycols are employed in various industrial hydraulicfluid applications. They generally do not dissolve rubber and find useas rubber lubricants or as textile fiber lubricants in textileprocessing. Because they decompose into volatile products at hightemperatures they also find use in once-through lubrication systems suchas in jet aircraft engines and other high temperature operations thatwould result in depositing carbonaceous materials on the moving surfacesand consequent operational and maintenance difficulties. Combining watersoluble polyglycols with water provides compositions for use inhydraulic applications such as die casting machines, furnace controls,electric welders, and navy hydraulic catapults, as well as equipmenthandling for missiles.

[0036] The phosphate lubricants find use in fire resistance applicationsand generally comprise triaryl or trialkyl phosphates. Fire resistanceapplications include die casting machines, aircraft hydraulic fluids,air compressor lubricants and various naval and industrial systems.Blending the phosphates with chlorinated biphenyls provides hydraulicstability.

[0037] Polymerization of isobutylene containing smaller amounts of1-butene and 2-butene provides polybutylene lubricants ranging inviscosity from 5 to over 600 centistokes at 210°F with a chain length offrom about 20 to greater than about 100 carbon atoms. Polyisobutylenesfind application in high temperature apparatus such as conveyors, ovens,dryers and furnaces since they decompose and oxidize substantially toentirely volatile by-products leaving no carbon residue contrary topetroleum based lubricants. They find use in electrical transformers,cables, and refrigerator compressors with the higher viscosity gradesemployed as viscosity-index additives in petroleum lubricants.

[0038] Polyphenyl ethers or polyphenoxy polymers, with the ether groupin the three phenyl position in the polymer chain find use in hightemperature applications such as jet engines and hydraulic systems sincethey exhibit temperature stability at about 500°F.

[0039] Silicate ester high temperature hydraulic fluids generallycomprise tetra (2-ethylhexyl) and tetra (2-ethylbutyl) silicates as wellas the so-called dimer silicates such as hexa (2-ethylbutoxy)disiloxane.

[0040] Chlorinated bi-phenyl fluids provide fire resistance forlubricating fluids and hydraulic fluids.

[0041] Fluorocarbons such as polychlorotrifluoroethylene and copolymersof perfluoroethylene perfluoropropylene non-solid lubricants providehigh oxidation resistance in lubricating liquid oxygen and hydrogenperoxide manufacturing and handling equipment.

[0042] Greases

[0043] Greases comprise high viscosity lubricating fluids, made bycombining a petroleum or synthetic lubricating fluid with a thickeningagent. The thickeners generally comprise fattysoaps of lithium, calcium,strontium, sodium, aluminum, silica gel, and barium. The greaseformulation may also include coated clays such as bentonite andhectorite clays coated with quaternary ammonium compounds. Sometimescarbon black is added as a thickener to improve high-temperatureproperties of petroleum and synthetic lubricant greases. The addition oforganic pigments and powders which include arylurea compoundsindanthrene, ureides, and phthalocyanines provide high temperaturestability.

[0044] Grease additives generally fall into the same category as theadditives employed in petroleum lubricants including amine, phenolic,phosphite, sulfur, and selenium oxidation inhibitors. Amine deactivatorsare also employed where copper staining would be a problem or wherecopper would tend to promote catalytic oxidation. Amine salts, metalsulfonates, metal naphthenates, esters, and nonionic surfactants provideadded water resistance, and some protection against salt-spraycorrosion.

[0045] Greases employed in gear applications or sliding surfaceapplications contain extremeadditives such as lead soaps, sulfur,chlorine and phosphorous additives as described above. Adding solidpowders such as graphite, molybdenum disulfide, asbestos, talc, and zincoxide provides boundary lubrication.

[0046] Glycerol stabilizes the soap structure when used in combinationwith small amounts of water as well as dimethylsilicone oil to minimizefoaming.

[0047] Formulating the foregoing synthetic lubricants with thicknersprovides specialty greases and include, without limitation, polyglycol,diester, silicone-diester, polyester, and silicone lubricants.Nonmelting thickeners are especially preferred such as copperphthalocyanine, arylureas, indanthrene, and organic surfactant coatedclays. The organic esters and the silicone greases are generallyemployed in military applications especially for high temperature use.

[0048] The mechanical properties of greases have been measured and thosematerials having a NLGI number from 0 to 6 characterize these greases.

[0049] Solid Lubricants

[0050] Solid lubricants include inorganic compounds, organic compounds,and metal in the form of films or particulate materials to providebarrier-layer type of lubrication for sliding surfaces. These materialsare substantially solid at room temperature and above, but in someinstances will be substantially liquidus above room temperature.

[0051] The inorganic compounds include materials such as cobaltchloride, molybdenum disulfide, graphite, tungsten disulfide, mica,boron nitride, silver sulfate, cadmium chloride, cadmium iodide, boraxand lead iodide. These compounds exemplify the so-called layer-latticesolids in which strong covalent or ionic forces form bonds between atomsin an individual layer while weaker Van der Waal's forces form bondsbetween the layers. They generally find use in high temperatureapplications because of their high melting points, high thermalstabilities in vacuum, low evaporation rates, and good radiationresistance. Especially suitable materials include formulated graphiteand molybdenum disulfide. Both molybdenum disulfide and graphite havelayer-lattice structures with strong bonding within the lattice and weakbonding between the layers. Sulfur-molybdenum-sulfur lattices formstrong bonds whereas weak sulfur-sulfur bonds between the layers alloweasy sliding of the layers over one another. Molybdenum disulfide andgraphite are therefore especially important solid inorganic lubricants.

[0052] The particulate solid materials are formulated as colloidaldispersions in either water, wax, wax emulsions, petroleum oil, castoroil, mineral spirits. The solid non-particulate materials may beemployed as solutions in solvents selected to dissolve the solids toform a substantially liquidus composition at room temperature. Thesesolutions in turn can be made into emulsions as described herein,especially water emulsions. Where solvents are unavailable or difficultor expensive to use, the solid lubricants are used as particulates.

[0053] The emulsions, as that term is used herein, are either water inoil or oil in water emulsions, or oil in oil emulsions where thesolution is either the continuous or discontinuous phase. Waterdispersions are used for lubricating dies, tools, metal-working molds,oxygen equipment and in wire drawing.

[0054] Graphite-water dispersion used as a lubricant lose water due toevaporation, which is a disadvantage. Mixing the graphite with cadmiumoxide or molybdenum disulfide overcomes this.

[0055] Other suitable inorganic materials that do not have thelayer-lattice structure include basic white lead or lead carbonate, zincoxide, and lead monoxide.

[0056] Dispersing the inorganic compounds in various liquids such aslower molecular weight alcohols, glycols, petroleum oils, syntheticoils, and water, provides compositions used in airframe lubrication,fastenings such as nuts and bolts or screws, gears, wire drawing, andlubricating fittings.

[0057] Solid organic lubricant compounds comprise high melting organicpowders such as phenanthrene, copper phthalocyanine, and mixtures withinorganic compounds and/or other lubricants. Copper phthalocyanineadmixed with molybdenum disulfide comprises a good roller bearinglubricant.

[0058] The metal lubricants generally comprise soft metals such asgallium, indium, thallium, lead, tin, gold, silver, copper and the GroupVIII noble metals, ruthenium, rhodium, palladium, osmium, iridium, andplatinum. Forming these metal lubricants into particulate dispersions ina fluid and especially a liquid such as a liquid lubricant as describedherein including petroleum oils, synthetic oils, and water provideseasily applied lubricant compositions. Chalcogenides of the non-noblemetals may also be employed, especially the oxides, selenides, orsulfides.

[0059] Combining the solid lubricants with various binders keeps them inplace on the moving surface. Binders are especially necessary in drylubricant applications employing solid or particulate lubricants, andare sometimes described as bonded solid lubricants. Variousthermosetting and thermoplastic and curable binder systems includephenolic, vinyl, acrylic, alkyd, polyurethane, silicone, and epoxyresins. It would be an advantage, however, to provide a novel binderthat performed in the same way or improved on the function of thesebinders.

[0060] These types of coatings find application as lubricants forfasteners and bolt assemblies. The solid lubricants employed in thelatter application usually include silver, nickel, copper, molybdenumdisulfide, lead, or graphite.

[0061] Metal Working Lubricants

[0062] Metal working is another important area of lubrication metalworking which generally comprises operations involving machining,grinding, honing, lapping, stamping, blanking, drawing, spinning,extruding, molding, forging, and rolling.

[0063] The lubricants employed generally comprise water, mineral oils,fatty oils, and fatty acids, waxes, soaps, various chemical compounds,minerals, and synthetic lubricants as described herein. Some of theforegoing materials will be at a disadvantage because they do not havethe proper sticking properties or viscosity properties to remain inplace on the metal surfaces during working and accordingly have to beformulated to assure that they will be in place during the metal workingoperation. The addition of synthetic polymers to these lubricants wouldovercome some of these disadvantages.

[0064] Lubricants are also described by Kirk-Othmer Encyclopedia ofChemical Technology, Second Edition, pp. 559-595 which is incorporatedherein by reference.

[0065] For the purpose of the present invention, all of the foregoinglubricant compounds or composition will be referred to as materials fordecreasing friction between moving surfaces or lubricants.

[0066] From the foregoing, it should be apparent that there is a needfor additional materials that will provide the same advantages as thoseof the related art as well as additional advantages and also materialsthat will overcome some of the various disadvantages of the related art.

[0067] Accordingly, the present invention is directed to a novelcomposition which includes a material for decreasing friction betweenmoving surfaces as well as a method for lubricating a surface.

[0068] Summary of the Invention

[0069] These and other advantages are obtained according to the presentinvention, which is the provision of a composition and a process toenhance the various advantages of the related art and which alsosubstantially obviate one or more of the limitations and disadvantagesof the described prior compositions of matter and processes.

[0070] The description which follows sets forth additional features andadvantages of the invention, apparent not only from the description, butalso by practicing the invention. The written description and claimshereof particularly point out the objectives and other advantages of theinvention and show how they may be realized and obtained.

[0071] To achieve these and other advantages, and in accordance with thepurpose of the invention, as embodied and broadly described, theinvention comprises a lubricant composition of matter comprising asuperabsorbent polymer combined with a material for decreasing frictionbetween moving surfaces or a lubricant as described herein. Where thelubricant is water or a petroleum oil, the composition also includes anadditive such as described herein including without limitation, anoxidation inhibitor, a rust inhibitor, antiwear agent,detergent-dispersant, pour-point depressant, viscosity-index improver orfoam inhibitor, especially those described herein.

[0072] The invention also comprises a method of lubricating a surfacecomprising coating the surface with a lubricating composition comprisinga superabsorbent polymer combined with a material for decreasingfriction between moving surfaces as described herein; however, themethod of the invention includes the use of water or oil as lubricantsas well as other lubricants either with or without additives asdescribed herein.

[0073] Throughout the written description and claims, the lubricantcomposition is described as a superabsorbent polymer combined with amaterial for decreasing friction between moving surfaces or lubricant,by which it is intended that the superabsorbent polymer and thelubricant either form a solution, a dispersion, or an emulsion includingboth water in oil emulsions as well as oil in water emulsions, and oilin oil emulsions wherein a solution is emulsified, and where thesolution can be the continuous phase or the discontinuous phase.

[0074] The superabsorbent polymer employed according to the invention,absorbs from about 25 to greater than 100 times its weight in water andcomprises a polymer of acrylic acid, an acrylic ester, acrylonitrile oracrylamide, including co-polymers thereof or starch graft copolymersthereof, or mixtures thereof, where the mixtures contain from 2 to about3 or 4 superabsorbent polymers.

[0075] Superabsorbent polymers that may be employed in the presentinvention comprise those generally described and those specifically setforth by Levy in United States Patents Nos. 4,983,389, 4,985,251, andparticularly those described in U.S. Patent No. 4,983,389, in column 9,lines 37-48, column 10, lines 40-68, and column 11, lines 1-21 as wellas those also described in U.S. Patent No. 4,985,251, column 9, lines1-30. The various U.S. patents to Levy, are incorporated herein byreference for their teachings relative to the superabsorbent polymers.

[0076] Other superabsorbent polymers include Aquasorb® which arecopolymers of acrylamide and sodium acrylate or the potassium orammonium salts thereof; Aquasorb® which are acrylamide-sodiumpolyacrylate cross-linked copolymers; Aquastore™ which is an ionicpolyacrylamide, and cross-linked modified polyacrylamides, Terra-Sorb™which is a hydrolyzed starch-polyacrylonitrile; Sanwet® which is astarch-graft-sodium-polyacrylate, or a polyurethane withstarch-graft-sodium polyacrylate, starch-graft-sodium polyacrylate,starch, polymer with 2-propenoic acid, sodium salt, WATER LOCK® which isa poly-2-propenoic acid, sodium salt, and a starch-g poly(2-propenamide-co-2-propenoic acid, sodium salt) or mixed sodium andaluminum salts or potassium or a 2-propenoic acid, sodium salt orpolyacrylamide-co-sodium acrylate); Aquakeep® which is a polyacrylicacid, sodium salt, Agri-GeJ™ which is an acrylonitrile starch graftcopolymer, SGP® 502S which is a starch-g-poly (acrylamide-co-sodiumacrylate Stockosorb® which comprise acrylate/acrylamide copolymers,acrylate/polyvinyl alcohol copolymers, and polyacrylates, and thevarious sodium and potassium salts thereof, Favor® C which is apotassium polyacrylate/polyacrylamide copolymer; XU 40346.00 from DowChemical which is a partial sodium slat of cross-linked polypropenoicacid; ASAP™ 1000 which is a reaction product of lightly cross-linkedsodium polyacrylate in water with hydrophobic amorphous silicon dioxide,and acrylic acid, Aridall™ which are sodium or potassium polyacrylatesthat may be lightly cross-linked SANWET® which is a starch graftedsodium polyacrylate NORSOCRYL® which is a poly(sodium acrylate)homopolymer, and ALCOSORB™ which is a copolymer of acrylamide and sodiumacrylate, and the various superabsorbent polymers described by Takeda etal. U.S. Patent No. 4,525,527; Mikita et al. U.S. Patent No. 4,552,938;U.S. Patent No. 4,618,631; Mikita et al. U.S. Patent No. 4,654,393;Alexander et al. U.S. Patent No. 4,677,174; Takeda et al. U.S. PatentNo. 4,612,250; Mikita et al. U.S. Patent No. 4,703,067; andBrannon-Peppas, Absorbent Polymer Technology, 1990. Other superabsorbentpolymers may be employed which are further described by Buchholz et al.,Superabsorbent Polymers, Science and Technology, 1994 ACS. All of theforegoing are incorporated herein by reference.

[0077] In one embodiment, the material for decreasing friction comprisesa petroleum lubricant containing an additive, water containing anadditive, synthetic lubricant, grease, solid lubricant or metal workinglubricant, wherein said synthetic lubricant, grease, solid lubricant ormetal working lubricant optionally contain an additive. Lubricating oilsinclude either a petroleum oil or synthetic oil or synthetic organicliquid as described herein including without limitations petroleumlubricants including the paraffins, aromatics, naphthenic oils, thesynthetic oils, including the silicones, organic esters, polyglycols,phosphates, polyisobutylenes, polyphenol ethers, silicates, chlorinatedaromatics, and fluorocarbons all as described herein.

[0078] The greases, solid lubricants, and metal working lubricants arealso as described herein.

[0079] Various mixtures of each of the foregoing lubricants may be usedincluding mixtures of 2 to about 3 or about 4 lubricants.

[0080] As noted before, additives described herein are also employedaccording to the invention. The composition of matter includes additiveswhere petroleum oil or water is used as a lubricant, whereas the methodof the invention of lubricating a surface includes the use ofsuperabsorbent polymers in combination with the lubricants describedherein, with or without the additives.

[0081] The material for decreasing friction between moving surfaces orlubricant employed according to the present invention also includeswater or combinations of water and oil whether petroleum oils orsynthetic oils as those materials are described herein. When water isused in combination with oil, it generally is employed as an emulsionwhether a water in oil emulsion or an oil in water emulsion, both ofwhich are well known in the art and are manufactured by methods that aresimilarly well known.

[0082] The invention also relates to a superabsorbent polymer combinedwith a solid or particulate inorganic lubricant such as those describedherein including mixtures of solid or particulate inorganic lubricantsespecially mixtures of 2 to about 3 or about 4 solid or particulateinorganic lubricants.

[0083] In one embodiment, these inorganic lubricants comprise graphite,the chalcogenides of molybdenum, antimony, niobium, and tungsten, wherethe chalcogens comprise oxygen, sulfur, selenium, and tellurium andespecially molybdenum disulfide, cobalt chloride antimony oxide, niobiumselenide, tungsten disulfide, mica, boron nitride, silver sulfate,cadmium chloride, cadmium iodide, borax, basic white lead, leadcarbonate, lead iodide, asbestos, talc, zinc oxide, carbon, babbit,bronze, brass, aluminum, gallium, indium, thallium, thorium, copper,silver, gold, mercury, lead, tin, indium, or the Group VIII noblemetals.

[0084] Chalcogenides of the nonmetals may also be employed, especiallythe oxides, selenides or sulfides. In another embodiment, the inorganicsolid or particulate material comprises a phosphate such as a zincphosphate, iron phosphate, or manganese phosphate, or mixtures thereof.Mixtures of the solid or particulate lubricants can be used, especiallythe 2 component 3 or about 4 component mixtures.

[0085] The superabsorbent polymers are also combined with a solid orparticulate organic lubricant including mixtures of the organiclubricant and especially 2 to about 3 or about 4 component mixtures.

[0086] The solid or particulate organic lubricant comprisesphenanthrene, copper phthalocyanine, a fluoroalkylene homopolymer orcopolymer such as polytetrafluoroethylene, polyhexafluoroethylene, orcopolymers of perfluoroethylene and perfluoropropylene. Homopolymers ofpolyvinylidene fluoride or copolymers of polyvinylidene fluoride andhexafluoropropylene may also be employed as well as other fluorinatedpolymers which are well-known in the art. The solid or particulateorganic lubricant may also include alkylene homopolymers or copolymerssuch as polymers of ethylene, propylene, isopropylene, butylene, andisobutylene and the various copolymers thereof especially the 2 or 3component copolymers thereof. The solid or particulate organic lubricantmay also include a paraffinic hydrocarbon wax. Various mixtures of thesolid or particulate organic lubricants may also be employed, especiallythe 2 to about 3 or about 4 component mixtures.

[0087] Combinations of the solid or particulate inorganic lubricant andthe solid or particulate organic lubricant can also be employed,especially the 2 to about 3 or 4 component combinations. Both the solidor particulate inorganic lubricant and the solid or particulate organiclubricant may also be combined with room temperature liquid materialsfor decreasing friction between moving surfaces such as oil lubricantsand/or synthetic lubricants as described herein or water or combinationsof water and oil (including the synthetic lubricants) as describedherein.

[0088] The solid or particulate inorganic lubricant or solid orparticulate organic lubricant can also be used in combination with thesuperabsorbent polymers either as a mixture of powdered super absorbentpolymer with solid or particulate organic lubricant or where thesuperabsorbent polymer is admixed with water or oil or both as describedherein.

[0089] The superabsorbent polymer is also combined with a material fordecreasing friction which comprises a metal working lubricant containingwater or an emulsion of oil and water where the oil is either apetroleum oil or synthetic oil but especially a mineral oil and theemulsion comprises either a water in oil or an oil in water emulsion,the petroleum oils, and synthetic oils having been described herein. Themetal working lubricant containing water may also comprise a solid orparticulate inorganic or organic lubricant and water where the solid orparticulate lubricants are as described herein.

[0090] The lubricant compositions of the present invention and thelubricant compositions used according to the method of the invention maycomprise room temperature liquid compositions having SAE viscosities asdescribed herein or may have the consistency of grease as that term andthose consistencies are described herein.

[0091] Throughout the written description and claims, the lubricant isdescribed as a material for decreasing friction between moving surfacesby which it is meant that the material comprises either a compound orcomposition of matter or mixtures of a compound and a composition ofmatter.

[0092] The average particle size of the particulate inorganic lubricantor organic lubricant or the superabsorbent polymer may be anywhere fromabout 0.001 in. to about 0.3 in. and especially from about 0.005 in. toabout 0.2 in. The superabsorbent polymer (as well as the lubricantcomposition) may also be in the form of flakes or sheets.

[0093] The lubricant composition can be either a liquid, including aviscous liquid, or gel, or a solid, whether rigid, semi-rigid orflexible at room temperature. Solid lubricant compositions also includea powdered lubricant composition. One of the outstanding features of thelubricant composition is that it can be shaped by any conventionalmolding or extruding process to form discs, sheets, rods, blocks,powders, or filaments, and especially solid lubricant compositions thatcan be formed to the contours of the surface or surfaces that are beinglubricated.

[0094] Additionally, multiple dry films of the same or differentlubricant composition may also be prepared, i.e. laminar structurelubricants where the layers of the laminate are anywhere from about 2 toabout 25 mils thick. These laminates may also have some laminar layersbased only on the superabsorbent polymer, or the lubricant, and thebalance on the lubricant composition. Additionally, the same ordifferent lubricant composition laminar layers may be used.

[0095] The superabsorbent polymer is used in combination with thelubricant in an amount anywhere from about 0.001 wt% to about 99 wt%,and especially from about 0.1 wt% to about 85 wt%, or from about 0.2 wt%to about 75 wt%, based on the combination of lubricant (with or withoutlubricant additives, or other additives) and superabsorbent polymer. Inone experiment, the superabsorbent polymer was combined with about 350times its weight of powdered graphite. Powders having an averageparticle size of about 325 mesh are taken up by some of thesuperabsorbent powders.

[0096] The lubricant and additives, when employed, are combined with thesuperabsorbent polymer by swelling the polymer either by itself ordispersed with the lubricant (and additives when employed), either inwater or in a high humidity environment, e.g. 80% R.H.

[0097] Prior to, or after exposing the superabsorbent polymer to wateror humidity, the polymer, in the form of a powder, flakes or granules ismixed with the lubricant in a conventional mixer, such as a HOBART™mixer until a uniform dispersion is obtained. This process may befacilitated by employing a solvent or dispersant for the lubricant,preferably in some instances, one that will be easily driven off fromthe lubricant composition of the invention, such as a ketone, especiallythe lower alkyl ketones e.g. acetone MEK, MIBK, DIBK, and the like.

[0098] The lubricant then combines with, or is taken up by thesuperabsorbent polymer that has been swollen with water. The lubricantcomposition is then dried to remove the water, for example by placing itin a 27-38% R.H. environment, or under vacuum or at elevatedtemperatures. This removes substantially all of the water introduced inthe first part of the process.

[0099] The lubricant composition, prior to removal of water as describedherein, or after removal of water is shaped by molding or extruding, andin the case of forming powdered or granular lubricants, is ground tomesh in a conventional grinding mill after the water has been removed.

[0100] Another outstanding feature of the lubricant compositions istheir ability, under pressure to release the lubricant as a film ordrop, or droplets, such as microdroplets and to recapture the releasedlubricant after pressure is released or ceases. The superabsorbentpolymers of the lubricant compositions in this regard were discovered tohave sponge like properties, even though no sponge like characteristics,such as porosity is visible to the naked or unaided eye, when examiningthe lubricant compositions.

[0101] A lubricant composition was made in the foregoing manneremploying graphite, as noted above, or a 2 mol ethoxylate of isostearylalcohol (AROSURF™ 66 E2). Although the latter is used as a surfactant,it also has some lubricating characteristics and is to be considered asa lubricant as well for the purpose of the present invention.

[0102] Other solid fillers, adjuvants and diluents can be used incombination with the lubricants employed in the lubricant composition ofthe present invention, including surfactants, liquid extenders, solventsand the like.

[0103] It will be apparent to those skilled in the art that variousmodifications and variations can be made to the lubricant composition ofthe present invention comprising a superabsorbent polymer in combinationwith a material for decreasing friction between surfaces as well as themethod for lubricating a surface employing such a composition withoutdeparting from the spirit or scope of the invention. It is intended thatthese modifications and variations of this invention are to be includedas part of the invention, provided they come within the scope of theappended claims and their equivalents.

Claims
 1. A method of lubricating a first surface that frictionallyengages a second surface by coating said first surface with alubricating composition having a superabsorbent polymer combined with amaterial for decreasing friction between moving surfaces.
 2. The methodof claim 1 of lubricating a first surface that frictionally engages asecond surface by coating said first surface with a lubricatingcomposition consisting essentially of a superabsorbent polymer combinedwith a material for decreasing friction between moving surfaces, wheresaid superabsorbent polymer absorbs greater than about 100 times itsweight in water and is a polymer of acrylic acid, an acrylic ester,acrylonitrile, acrylamide, co-polymers thereof or mixtures thereof,wherein said material for decreasing friction is a petroleum oillubricant or grease thereof, and wherein said material for decreasingfriction optionally contains a lubricant additive, wherein saidlubricant additive is an antioxidant, rust inhibitor, antiwear compound,extreme pressure additive, detergent, dispersant, pour point depressant,viscosity-index improver, or foam inhibitor.
 3. The method of claim12 oflubricating a first surface that frictionally engages a second surfaceby coating said first surface with a lubricating composition consistingessentially of a superabsorbent polymer combined with a material fordecreasing friction between moving surfaces, where said superabsorbentpolymer absorbs greater than about 100 times its weight in water and isa polymer of acrylic acid, an acrylic ester, acrylonitrile, acrylamide,co-polymers thereof or mixtures thereof, wherein said material fordecreasing friction is a solid lubricant, wherein said solid lubricantis an inorganic compound, carbon, or metal that provides barrier-layerlubrication, and wherein said material for decreasing frictionoptionally contains a lubricant additive, wherein said lubricantadditive is an antioxidant, rust inhibitor, antiwear compound, extremepressure additive, detergent, dispersant, pour point depressant,viscosity-index improver, or foam inhibitor.
 4. The method of claim 3wherein said solid lubricant is graphite, molybdenum disulfide, cobaltchloride, antimony oxide, niobium selenide, tungsten disulfide, mica,boron nitride, silver sulfate, cadmium chloride, cadmium iodide, borax,basic white lead, lead carbonate, lead iodide, asbestos, talc, zincoxide, carbon, babbitt, bronze, brass, aluminum, gallium, indium,thallium, thorium, copper, silver, gold, mercury, lead, tin, indium, orthe Group VIII noble metals or mixtures thereof.
 5. The method of claim1 of lubricating a first surface that frictionally engages a secondsurface by coating said first surface with a lubricating compositionconsisting essentially of a superabsorbent polymer combined with amaterial for decreasing friction between moving surfaces, where saidsuperabsorbent polymer absorbs greater than about 100 times its weightin water and is a polymer of acrylic acid, an acrylic ester,acrylonitrile, acrylamide, co-polymers thereof or mixtures thereof,wherein said material for decreasing friction is a solid organiclubricant, and wherein said material for decreasing friction optionallycontains a lubricant additive, wherein said lubricant additive is anantioxidant, rust inhibitor, antiwear compound, extreme pressureadditive, detergent, dispersant, pour point depressant, viscosity-indeximprover, or foam inhibitor.
 6. The method of claim 5 wherein said solidorganic lubricant is a fluoroalkylene homopolymer or copolymer, a loweralkylene polyolefin homopolymer or co-polymer, a paraffinic hydrocarbon,wax, phenanthrene, copper phthalocyanine, or mixtures thereof.
 7. Themethod of claim 1 of lubricating a first surface that frictionallyengages a second surface by coating said first surface with alubricating composition consisting essentially of a superabsorbentpolymer combined with a material for decreasing friction between movingsurfaces, where said superabsorbent polymer absorbs greater than about100 times its weight in water and is a polymer of acrylic acid, anacrylic ester, acrylonitrile, acrylamide, co-polymers thereof ormixtures thereof, wherein said material for decreasing friction is wateroptionally containing a lubricant additive, wherein said lubricantadditive is an antioxidant, rust inhibitor, antiwear compound, extremepressure additive, detergent, dispersant, pour point depressant,viscosity-index improver, or foam inhibitor.
 8. The method of claim 7wherein said material for decreasing friction is an oil, or greasesthereof, and water.
 9. The method of claim 7 wherein said material fordecreasing friction is a solid lubricant and water.
 10. The method ofclaim 9 wherein said solid lubricant is graphite, molybdenum disulfide,cobalt chloride, antimony oxide, niobium selenide, tungsten disulfide,mica, boron nitride, silver sulfate, cadmium chloride, cadmium iodide,borax, basic white lead, lead carbonate, lead iodide, asbestos, talc,zinc oxide, carbon, babbit, bronze, brass, aluminum, gallium, indium,thallium, thorium, copper, silver, gold, mercury, lead, tin, indium, theGroup VIII noble metals, a fluoroalkylene homopolymer or copolymer, alower alkylene polyolefin homopolymer or co-polymer, a paraffinichydrocarbon, wax, phenanthrene, copper phthalocyanine, or mixturesthereof.
 11. The method of claim 1 of lubricating a first surface thatfrictionally engages a second surface by coating said first surface witha lubricating composition consisting essentially of a superabsorbentpolymer combined with a material for decreasing friction between movingsurfaces, where said superabsorbent polymer absorbs greater than about100 times its weight in water and is a polymer of acrylic acid, anacrylic ester, acrylonitrile, acrylamide, co-polymers thereof ormixtures thereof, wherein said material for decreasing friction is aphosphate, and wherein said material for decreasing friction optionallycontains a lubricant additive, wherein said lubricant additive is anantioxidant, rust inhibitor, antiwear compound, extreme pressureadditive, detergent, dispersant, pour point depressant, viscosity-indeximprover, or foam inhibitor.
 12. The method of claim 10 wherein saidmaterial for decreasing friction is zinc phosphate, iron phosphate ormanganese phosphate, or mixtures thereof.
 13. The method of claim 1 oflubricating a first surface that frictionally engages a second surfaceby coating said first surface with a lubricating composition consistingessentially of a superabsorbent polymer combined with a material fordecreasing friction between moving surfaces, where said superabsorbentpolymer absorbs greater than about 100 times its weight in water and isa polymer of acrylic acid, an acrylic ester, acrylonitrile, acrylamide,co-polymers thereof or mixtures thereof, wherein said material fordecreasing friction is a fatty oil, fatty acid or wax, and wherein saidmaterial for decreasing friction optionally contains a lubricantadditive, wherein said lubricant additive is an antioxidant, rustinhibitor, antiwear compound, extreme pressure additive, detergent,dispersant, pour point depressant, viscosity-index improver, or foaminhibitor.
 14. The method of claim 1 of lubricating a first surface thatfrictionally engages a second surface by coating said first surface witha lubricating composition consisting essentially of a superabsorbentpolymer combined with a material for decreasing friction between movingsurfaces, where said superabsorbent polymer absorbs greater than about100 times its weight in water and is a polymer of acrylic acid, anacrylic ester, acrylonitrile, acrylamide, co-polymers thereof ormixtures thereof, wherein said material for decreasing friction is asynthetic oil lubricant, or grease thereof, and wherein said materialfor decreasing friction optionally contains a lubricant additive,wherein said lubricant additive is an antioxidant, rust inhibitor,antiwear compound, extreme pressure additive, detergent, dispersant,pour point depressant, viscosity-index improver, or foam inhibitor. 15.The method of claim 1 of lubricating a first surface that frictionallyengages a second surface by coating said first surface with alubricating composition consisting essentially of a superabsorbentpolymer combined with a material for decreasing friction between movingsurfaces, where said superabsorbent polymer absorbs greater than about100 times its weight in water and is a polymer of acrylic acid, anacrylic ester, acrylonitrile, acrylamide, co-polymers thereof ormixtures thereof, wherein said material for decreasing friction is asoap, and wherein said material for decreasing friction optionallycontains a lubricant additive, wherein said lubricant additive is anantioxidant, rust inhibitor, antiwear compound, extreme pressureadditive, detergent, dispersant, pour point depressant, viscosity-indeximprover, or foam inhibitor. 15.